Method of making nanocomposite dispersions for use as coatings for packaging material by exfoliating a mineral filler in a solvent with process parameter chosen to produce lamellae with a high form factor

摘要

A method of making a nanocomposite dispersion comprising a solvent, a resin dispersible or soluble in the solvent and a nanoparticulate filler based on an exfoliated phyllosilicate, intended to be applied to a support, by exfoliating the filler, at a specified shear rate and dispersing it in the solvent to a specified concentration and viscosity for sufficient time to exfoliate at least 50% of the filler. The mineral filler is dispersed by a means of exfoliation, at a shear rate below the maximum, into the solvent to a concentration less than the maximum and typically 1-10 wt.% and with a viscosity lower than the maximum, so as to obtain a nanoparticulate dispersion of exfoliated lamellae. The filler is pre-selected with reference to the solvent and the maximum shear, concentration and viscosity so determined in advance as to obtain, at a high productivity level, a fluid dispersion comprising lamellae having a high average form factor, which is close to that of the initial material. The resin is then incorporated at 10-60 wt.% for sufficient time to ensure that 95% of the resin is dispersed with a particle size below that of the thickness of the nanocomposite layer, typically 5 mu m. The dispersion is typically applied to the support by coating and forms a layer comprising the exfoliated material. The stages or preparation of the dispersion and coating of the support form a continuous process. Independent claims are also included for: (1) The use of the method to transform any standard varnish or coating comprising a solvent and a resin into a nanocomposite dispersion; (2) A nanocomposite dispersion, obtained by the claimed method, comprising 0.5-5 wt.% filler and 10-60 wt.% resin and having a viscosity below 250 mPa.s under a shear of 100s-1 capable of being applied to a substrate on a reel by coating typically with a roller or by spraying; (3) A means of coating a support by applying the claimed dispersion, optionally diluted and/or incorporating additives, eliminating the solvent and optionally polymerizing the resin to obtain a nanocomposite coat with a thickness 1-5 mu m and a ratio of filler to resin of at least 80%; and (4) Coated substrates in which the resin is EVOH, vinyl, acrylic or nitrocellulosic.